In the non-patent literature 1 and the patent literature 1, an example of a conventional communication quality monitoring system is described.
The non-patent literature 1 describes a method of the technique that is referred to as the network tomography. In this method, a plurality of communication quality measuring apparatuses, each of which is referred to as a probe terminal, are installed on a network system for inferring a degradation point of a communication quality.
Further, in the patent literature 1, in order to enable monitoring of a large scale network system, a means is prepared, in which a tree-type network is assumed, and a delay cause portion is narrowed down for collecting the operational information of network apparatus in the cause portion.
Other than the above techniques, the non-patent literature 2 describes the OpenFlow framework as a new network framework.
The OpenFlow framework consists of OpenFlow switches and OpenFlow Controller. An OpenFlow switch inquires forwarding rules (rule and action) of a packet to an OpenFlow controller. An OpenFlow controller senses a network state, calculates communication paths of packets, determines forwarding rules of the packets, and then sets their forwarding rules into OpenFlow switches. An OpenFlow Controller and OpenFlow Switches are connected through a Secure Channel so that the OpenFlow Controller controls the OpenFlow Switch by using a control message based on an OpenFlow protocol. This enables a control algorithm, new ideas and the like are mounted thereon, to be easily applied to a network environment.
The OpenFlow Switches are edge switches and core switches, which are controlled by an OpenFlow controller in OpenFlow network. Flow shows a communication in specified path, which is a transfer from incoming a packet to the input side edge switch to sending it from the output side edge switch.
The forwarding rule is defined by various combinations of one or all of a destination address (Destination Address), a transmission source address (Source Address), a destination port (Destination Port) and a transmission source port (Source Port) that are included in the header region of each protocol hierarchy level in the packet and can be distinguish from other forwarding rules. In the above addresses, it is assumed that a MAC address (Media Access Control Address) and an IP address (Internet Protocol Address) are included. Further, in addition to the above, the information of an ingress port (Ingress Port) can be used as the transfer rule.
The action of the transfer rule indicates the operations such as “outputting to a particular port”, “discarding” and “rewriting of a header”. For example, if the identification information of an output port (the number of the output port or the like) is indicated in the action of a flow entry, the OpenFlow Switch outputs the packet to the port corresponding to the indication information, and if the identification information of the output port is not indicated, the OpenFlow Switch discards the packet. Or, if header information is indicated in the action of a flow entry, the OpenFlow switch rewrites the header of the packet on the basis of the header information.
The OpenFlow switch executes the action of the flow entry, for a packet group (a packet series) complying with the rule of the flow entry.
The details of the OpenFlow technique are described in the non-patent literature 3.
In the non-patent literature 4, a network tomography technique that uses this OpenFlow Framework is described. In the non-patent literature 4, since a monitoring route can be set, a route for comprehensively monitoring the network from a small number of probe terminals is determined, set, and monitored, and consequently, the communication quality can be monitored by the small number of probe terminals.
A problem of conventional monitoring systems is the high monitoring cost. This is caused by the fact that in many monitoring systems, a monitoring function must be installed for all of the terminals and all of the edge terminals in the network. Further, many monitoring routes are required to be set for the respective monitoring functions. For example, though the technique described in the non-patent literature 4 has a merit that the monitoring function can be reduced, in order to enable the network to be comprehensively observed, many monitoring routes are required to be set, which leads to a result that many monitoring packets flow.
Moreover, because many monitoring routes are set, the network load for information synchronization and information collection is required.